Hydraulic lash adjusters are known to be useful in reducing lash, or extra clearance, in a valve train during operation of an internal combustion engine. A cam rotates and actuates a rocker arm to translate an engine valve to an open or closed position. A lash adjuster is disposed within the rocker arm and interfaces with the valve stem. The lash adjuster includes a follower body with a depending neck portion and enlarged diameter head portion. The head has a semispherical lower surface that is in rolling contact with a complementary socket in a foot member, allowing the foot member to swivel. Typically a retainer maintains the rolling contact by joining the foot member to the follower body. The means of retention is important to effect a permanent attachment that allows for sufficient swivel movement of the foot, while not complicating the manufacture of the components.
In some prior designs, a retainer is not used. Instead the design relies on valve spring preload to retain the foot in position. See U.S. Pat. No. 4,708,103. The disadvantage comes in assembling the separate foot and body into the engine. Also, upon disassembling the rocker arms, the foot portion may fall into the engine block.
When a retainer is part of the design, the retainer typically engages either or both the foot and the body of the adjuster through radial flanges or protrusions engaging a groove or indent. See U.S. Pat. Nos. 5,632,237 and 4,708,103. This approach requires additional machining of the foot to provide a receiver such as a groove or indent. Further the retainer cannot simply be drawn but requires shape changes to produce radial protrusions. Assembly is also disadvantaged if the foot and retainer must be oriented such that the protrusion and groove are aligned prior to assembly.